Encapsulation process for particles

ABSTRACT

Particles of a fluidizable substance are coated with a complete and continuous coating by a process wherein a non-aqueous solution of a coating substance is sprayed from a nozzle downwardly on a fluidized bed of the particles to be coated, the nozzle height being adjusted so that the liquid droplets of coating material would just cover the cross-sectional area of the upper surface of the bed, if sprayed on the unexpanded bed. When the aforementioned coating is a fatty acid having 12-20 carbon atoms applied to particles of a chlorine-releasing agent, and when a second coating is applied by treatment with a solution of a fixed alkali hydroxide, i.e., sodium, potassium, or calcium hydroxide, an effective, completely encapsulated, non-pinholing bleach product is obtained.

United States Patent Alterman et al.

[ Sept. 23, 1975 [5 ENCAPSULATION PROCESS FOR 3,671,296 6/1972 Funakoshiet al 117/100 B PARTICLES Primary ExaminerWilliam D. Martin [75]Inventors e r i' gg 13 8 i Assistant ExaminerDennis C. Konopacki f 3'} lge at 0t Attorney, Agent, or Firm-Kenneth F. Dusyn; James J. 0 Farrell;Arnold Grant [73] Assignee: Lever Brothers Company, New

York, NY. [57] ABSTRACT [22] Filed: Dec. 7, 1973 Particles of afluidizable substance are coated with a complete and continuous coatingby a process wherein [21] PP N05 422,813 a non-aqueous solution of acoating substance is sprayed from a nozzle downwardly on a fluidized bed[52] CI 427/213; 252/187 427/214. of the particles to be coated, thenozzle height being 427/337; 427/424; 428/403 adjusted so that theliquid droplets of coating material 51 int. c1. B05D 1/02; BOSD 1/36would Just cross-sectlonal area of the upper [58] Field of Search 117/100 B 621 167 surface of the bed, if sprayed on the unexpanded bed.

252/103 187 427/213 214 When the aforementioned coating is a fatty acidhaving 12-20 carbon atoms applied to particles of a chlo- [56]References Cited rine-releasing agent, and when a second coating isapplied by treatment with a solution of a fixed alkali hy- UNITED STATESPATENTS droxide, i.e., sodium, potassium, or calcium hydroxide, aneffective, completely encapsulated, non- 3 157 649 11/1964 252/187 cpinholing bleach product is obtained 3,382,093 5/1968 Nack 117/100 B 8Claims, 3 Drawing Figures amt 5,?

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H l/IAfE/(HAMKE P US Patent Sept. 23,1975 shw 2 of2 3,908,045

ENCAPSULATION PROCESS FOR PARTICLES BACKGROUND OF THE INVENTION 1. Fieldof the Invention The coating or encapsulation of discrete particulatematerial by a variety of processes is well known. In particular, the artis aware of many variations in processes for coating particulatematerial by a fluidized bed technique.

The present invention finds utility for applying either a completesingle coating or a double coating of a material to a particulatesubstance.

In the case ofa single coating, encapsulation methods known heretoforedo not always insure that the parti cles will have no adverse sideeffects during use.

The double coating process of the present invention is especiallyapplicable to the coating of particles of highly reactive substances.Most particularly the process finds utility in the detergent bleachfield wherein particulate fabric bleaching agents, such as potassiumdichloroisocyanurate, sodium dichloroisocyanurate, and the hydratesthereof are employed in home laundering operations as a dry bleachproduct to be added separately to a washing machine or for use inadmixture with particles of a detergent composition to form acommercially acceptable detergent-dry bleach combination. Because oftheir highly reactive nature the particles must not only be thoroughlyand imperviously coated to avoid contact of the bleach particles withthe detergent particles, but the coated particles must not attacktextile materials or the dyes thereon under washing conditions. Althoughprior-art processes may provide thorough and uniform coatings imperviousto potassium iodide solution, the coated particles of chlorinc-releasing compounds suffer the defect that they attack the dyesubstances at the points of contact with the fabric and have been knownto attack the fabric and make pinholes therein in a washing processwherein the coated bleach particles are placed directly on dry clothes.

2. The Prior Art Art that may be considered in connection with theinstant invention is represented by the patents listed below.

U.S. Pat. No. 1,950,956 to Wilhelm: Discloses the coat ing ofchloramine-T with stearic acid.

U.S. Pat. No. 1,480,561 to McNeil: Discloses a process wherein granulesare uniformly coated by dropping granules through a spray of a solutionof a coating substance and spraying the solution directly upon thegranules while they are being agitated in a tumbling mechanism.

U.S. Pat. No. 2,561,392 to Marshall: Relates to process and apparatusfor coating moving particles by spraying a solution of a coatingmaterial thereon. Provision is made to recirculate the particles toprovide a heavier coating. There is also disclosed a means for removingthe solvent from the coating material.

U.S. Pat. No. 2,579,944 to Marshall: Discloses a tandem coating systemwherein particles in a turbulent state are coated by spraying with asolution of a coating substance in a first chamber and sequentiallycoated by spraying with a solution of a second substance in a secondchamber. The patentee states in column 6, lines 18-22 that it isdesirable to have the sprayers adjustable vertically so as to coat theparti- -cles properly when the surface of the bed is changed.

US Pat. No. 2,594,469 to Mahoney: Relates to a process whereinparticles, such as spraydried detergent particles fall by gravity withina chamber, and the falling particles are coated by spraying with asolution of the coating substance.

U.S. Pat. No. 2,768,095 to Tadema et al.: Provides a method foruniformly distributing liquids in finely divided solids withoutsubstantial loss of materials. The liquid may be a solution of one ormore materials in a suitable solvent, and is injected within a fluidizedbed of the finely divided solids either counter to, or parallel to, thegas stream used for fluidization.

U.S. Pat. No. 3,650,961 to Hudson: Discloses a method for encapsulatingchlorocyanurates with hydratable inorganic salts. A fluidized bed of theinorganic salt is formed, on which is sprayed droplets of a slurry of achlorocyanurate, or other detergent adjunct. By controlling the dropletsize, the detergent is made to form the core material disposedpredominantly in the center of the particle, while the inorganic salt,partially hydrated, surrounds the core, and the particle size can becontrolled to about 10-100 mesh.

U.S. Pat. No. 3,671,296 to Funakoshi et al.: Particles are coated bytreatment with a liquid spray while the particles are circulating in acyclic pattern. Circulation is accomplished by moving the particles tothe outer edge of a rotating circular, horizontal dish, the force ofthis movement carrying the particles upward along the internal verticalsurface of a cylindrical or inwardly curved barrel, then leaving thebarrel surface to move toward the center of the barrel, thence fallingback to the revolving plate to repeat the circulating process.

SUMMARY OF THE INVENTION It has now been found that the problem ofinsuring complete encapsulation of a particulate material withoutagglomeration may be solved by applying a solution of a coatingsubstance to a fluidized bed of the particulate material, the nozzlefrom which the coating substance is sprayed being at a critical heightfrom the bed when in a static state.

It has moreover been found that the problem of pinholing, discussedhereinbefore, can be solved or greatly alleviated by applying to theparticles of the substance which can cause pinholing, i.e., a substancehaving at least one reactive chlorine atom in its molecular structure, afirst coating of a solidifiable saturated fatty acid, and sequentiallyapplying a second coating of soap by treating the first coating of fattyacid with a solution of a fixed alkali hydroxide selected from the groupcon sisting of sodium hydroxide, potassium hydroxide, and calciumhydroxide.

In a first embodiment, the present invention provides a granular,free-flowing, non-agglomerated, dry chlorinated bleach product for useduring the washing of textiles, wherein the granules are coated with asubstance which prevents reaction of the bleach product during storageand additionally prevents pinholing of the textiles and attack on thedyestuffs thereon.

It is therefore an object of the invention to apply a double coating toparticles of a chlorinated bleach substance.

It is another object of the invention to provide a coating system onparticles of a compound having releasable chlorine therein, wherebybleach damage (pinholing) on colored fabrics is prevented and goodchlorine release during the wash cycle is provided.

It is a further object of the invention to provide a coating compositionfor the above-described chlorinecontaining bleach compounds which isrelatively slow dissolving to prevent bleach damage on colored fabricsand to permit good chlorine release during the wash cycle.

In a second embodiment, the invention provides a process for depositinga complete and continuous single coating on a particulate substance in afluidized state.

The present invention is described herein in terms of potassiumdichloroisocyanurate, a well-known oxidant and household bleach, whichhas two reactive chlorine atoms per molecule, and readily releases thechlorine in an oxidizing action in contact with a reducible substance,or by hydrolysis in contact with water.

However, the particles which are advantageously coated by the process ofthe invention are not limited to the aforesaid potassiumdichloroisocyanurate, but may be any fluidizable substance inparticulate form.

DETAILED DESCRIPTION OF THE INVENTION In one aspect of the instantinvention there is provided a process wherein particles of achlorinereleasing agent are coated with a double layer of coatingsubstances as described hereinafter.

In another aspect the invention provides a process for applying a singlecoating substance to any fluidizable particulate material.

The products obtained by the process of the present invention areencapsulated, free-flowing, nonagglomerated particles having a core ofthe substance to be coated, a first or primary coat ofa solidifiablematerial, which may be the sole coat, and in the case of a coresubstance which is an oxidant having releasable chlorine in itsmolecule, the particles have a first coat of a saturated fatty acid anda second coat of a soap of the fatty acid.

A preferred product made by the process of the present invention isencapsulated potassium dichloroisocyanurate in particulate form, saidparticles having thereon an inner and an outer coating, said innercoating comprising a fatty acid from 12 to 20 carbon atoms, or mixturesthereof, and said outer coating comprising a sodium salt of said acid,or mixtures thereof, said particles of potassium dichloroisocyanuratehaving said inner coating being completely encapsulated by said sodiumsalt.

Most preferably, the encapsulated particles suitable for bleachingfabrics in an aqueous medium in accordance with the present inventioncomprise:

i. a core of potassium dichloroisocyanurate,

ii. a primary coating contiguous to said core of a fatty acid comprisingabout 55% palmitic acid and about 45% stearic acid, and

iii. an outer coating of the sodium salt of said fatty acid, saidprimary coating and said outer coating being substantially continuous.

The core substance may be any substance in particulate form which can befluidized. Suitable nonchlorinated substances are:

sodium perborate enzymes optical brighteners sodium acetyl salicylateantibacterial agents polyethylene glycol/terephthalate copolymers.

Among the chlorine-releasing substances suitable as core material, theremay be mentioned those oxidants capable of having their chlorineliberated in the form of free elemental chlorine under conditionsnormally used for detergent bleaching purposes, such as potassiumdichloroisocyanurate, sodium dichloroisocyanurate, chlorinated trisodiumphosphate, calcium hypochlorite, lithium hypochlorite, monochloramine,dichloramine, nitrogen trichloride, [(mono-trichloro)-tetra-(mono-potassium dichloro)]penta-isocyanurate,l,3-dichloro-5,5-dimethyl hydantoin, paratoluene sulfondichloroamide,trichloromelamine, N- chloroammeline, N-chlorosuccinimide, N,Ndichloroazodicarbonamide, N-chloro acetyl urea,

N,N-dichlorobiuret, chlorinated dicyandiamide, trichlorocyanuric acid,and dichloroglycoluril.

The instant invention is applicable to particulate substances having awide range of particle sizes, so long as the particles are fluidizable.Commonly, particles of 5 to I20 U.S. mesh size are employed.

When only a single coat is to be deposited by the process describedherein the coating substance may be a fatty acid, or may comprise suchsubstances as polyvinyl alcohol, polyvinyl pyrrolidone, polyethyleneglycols having a molecular weight from about 6,000 to about 16,000,copolymers of vinyl methyl ether and maleic anhydride, etc. The solventfor the coating substance will be selected with due regard for itsvolatility and inertness toward the core material. For example, methanolis a suitable solvent for depositing a coating of polyethylene glycol(6,000 molecular weight) on particles of sodium perborate. Preferablythe boiling point of the solvent is about F to about F. The capacity ofthe exhaust system will be considered in determining whether a solventhaving a boiling point in the upper portion of the foregoing range canbe used. For example, if relatively little solvent is required for thecoating substance, the boiling point can be higher than in instanceswherein a high proportion of solvent is needed.

When a dual coating is to be applied, it is essential that the firstcoating be a saturated fatty (alkanoic) acid which is solidifiable andwhich remains solid at temperatures likely to be encountered duringmanufacture or storage, for example, a temperature of about 85l30F.Suitable fatty acids are the well-known nalkanoic acids having fromabout 12 to about 20 carbon atoms. A particularly suitable fatty acid isEmersol 132 (trademark of Emery Industries, Inc.), which issubstantially 45% stearic acid and 55% palmitic acid and which melts atabout l31132F. The fatty acid is applied as a solution in a suitablesolvent, methylene chloride being preferred because of itscompatibility, non-reactivity with chlorine-releasing agents,nonflammability, and low toxicity.

Moreover, the fatty acid will be selected with due regard to its meltingpoint in relation to the use to which the coated particles are to beput. For example, in the case of a dual-coated product intended for useas a bleaching agent in a home laundering operation, the melting pointof the fatty acid may be somewhat higher than the temperature of thewash solution, but not so high that it is not removed from the core bythe emulsifying action of the outer soap layer.

The following fatty acids or mixtures thereof are suitable.

Numbcr of Carbon Atoms Approximate Melting Point, ()F

Laurie Acid I2 I l I Myristic Acid I4 I36 Palmitic Acid I6 I47 StearicAcid 18 157 Arachidic Acid 20 I69 Lin coating material, discharged in adownwardly diverging three-dimensional pattern, would if sprayed on thebed of particles in the unexpanded state, just cover the upper surfacearea of the bed, i.e., a right cross section of the spray pattern at thelevel of the upper surface of the unexpanded bed, is coincident inperipheral configuration therewith.

When the spray nozzle and the spray pattern of droplets issuingtherefrom are Conical, the nozzle location is such that the projectionof the nozzle cone surface intersects the tower wall at the level of theupper surface of the bed of particles when in the unfluidized state.

The coating solution is contained in vessel 6 and is fed to nozzle 5 bypump 7. The spraying of the coating Approximate Melting Potassiumdichloroisocyanurate, typical of the cyan urates suitable as coresubstances, is commerically available and may be obtained from theMonsanto Chemical Company. The chemical structure of this compound maybe represented by the graphic formula:

i N o :p cl: 0 CI-N N-CI Information regarding this and three relatedcompounds may be found in Monsanto Technical Bulletin I-l77.

The second coating is a sodium, potassium, or calcium salt of the fattyacid which comprises the firstcoat.

When carrying out the process of the instant invention, the firstcoating is conveniently applied by means of the apparatus shownschematically in FIGS. 1-3. Referring to the drawings, referencecharacter 1 indicates a chamber or cylindrical tower, wherein thecoating or encapsulation of the particles is accomplished. At the baseof tower 1 is supporting screen 2 (FIGS. 1 and 2). The tower is fittedwith a manifold inlet for the introduction of tangential air shown at 4.Shown at 3 is an unexpanded bed of the particles to be coated. Adownwardly projecting nozzle constituting a spraying means 5 isadjustably disposed within the tower l, and adapted to be adjustedvertically so that the liquid droplets of solution from nozzle 5 isaided by pressurized air entering tower 1 at 8. Fluidizing gas passesthrough duct 9 and is forced through the screen support by blower l0 andis either cooled by cooling system 13, or heated by heat exchanger 11,if required, in order to maintain the fluidizing gas within a criticaltemperature range. An exhaust blower 12 removes solvent vapors. It willbe recognized from the foregoing description that the height of thespray nozzle relative to the bed of particles in the static state iscritical to obtain the spray pattern required to deposit a complete andcontinuous coating on each particle. It has been found that theparticles are not adequately coated if there is any substantialdeviation in the spray pattern relative to the height of the static bed.

More fully described in terms of a specific embodiment of the apparatus,equipment suitable for carrying out the process of applying the first orsole coating on a particulate substance may comprise a vertical tower 1having appropriate dimensions, for example, a diameter of about 1 footand a height of about 5 feet comprising a coating chamber. The bottom ofthe unit contains a conical shape receptable for entering fluidizingair. The particulate matter is supported by a screen, grid, or porousplate having a sufficient number of openings to provide substantiallyeven distribution of the upward flowing gas over the cross section ofthe coating tower. All metal parts are fabricated of stainless steel.

It is preferred that the support on which the particle bed rests besubstantially a screen, e.g., having about 10 to about US. mesh openingsper inch, rather than a perforated plate with relatively few openings,to aid the circulation of every particle by the incoming air. Suitably a60-mesh screen may be used.

Fluidizing air enters the apparatus through a 6 inch diameter flexibleduct 9 below the supporting screen.

This air is supplied from a conventional air blower capable ofdelivering air at a superficial air velocity of from about 4-15 feet persecond and preferably from about 7l2 feet per second in the fluidizer.Provision has been made either to heat or cool the entering air asrequired by a steam heat exchanger 11 and a cooling unit 13. Inaddition, a small amount of air is supplied through a series of nine-%inch diameter tubing jets, equally spaced about the inner perimeter atthe support screen level. The function of the air jets is to helpprovide uniform particle coating by preventing any stagnant bed areasfrom forming at the wall.

Solutions of the coating material are pumped to a two-fluid atomizingnozzle 5 by a simplex reciprocal constant volume metering pump. Thenozzle head has at least two, and preferably six, holes so disposed asto spray the coating solution evenly over the entire cross sectionalarea of the fluidized bed. This particular spray pattern provides amaximum available coating zone. The nozzle can be located at variousheights above the support screen depending on the volume of corematerial in the bed. However, the most suitable location of the nozzleis the point at which the coating solution can be sprayed on the upperperimeter of the unfluidized bed core material.

The coating solution reservoir and pipe lines leading to the nozzle areheated in some cases to prevent solidification of the coating materialin solution. Flow meters are used to measure gas flow and this flow iscontrolled by conventional valves and gauges.

Air is exhausted through a blower 12 to a wash drum. A cyclone separatormay be used to recycle the smaller particles that have been elutriatedfrom the bed.

The fluidizer is fitted with two Plexiglas windows and a Plexiglas doorthat allow for observation during a run. The door also serves as a meansof filling and emptying the fluidizer of solid material.

In operation, a known weight of a multiplicity of particles to be coatedis placed on the perforated support, or supporting screen 2, in coatingtower 1. It is convenient to use a starting batch weight of to pounds ofuncoated particles.

Typically the thickness of the layer or bed in the static state is about1% to about 6 inches. The height of the spray nozzle 5 is adjusted to alevel such that the outermost droplets of the spray therefrom wouldcontact the layer of particles at the perimeter thereof as defined bythe layer in static state. Air is caused to flow upwardly by the forcecreated by blower 10 through duct 9, thereby expanding the thickness ofthe layer of particles, and maintaining the particles in continuousmotion within the volume defined by the expanded bed, thus forming afluidized bed 3.

A solution of a solidifiable coating substance, contained in vessel 6,is sprayed by means of pump 7 through nozzle 5 on the fluidized bed 3until all particles in the bed are completely coated. The time requiredfor a coating run in a l-foot diameter tower may vary from about 10minutes to about 2 hours, depending upon such factors as type ofcoating, concentration of coating solution, and the desired rate ofapplication of the coating solution.

It is critical to control the spray pattern as described hereinbefore,and to employ supplemental tangential air so as to insure adequatemovement and circulation of all the particles during fluidization and asa result to achieve a complete and continuous coating on all theparticles. A suitable spray nozzle is a Sprayco No. 26 nozzlemanufactured by the Spraying systems Co. This nozzle contains six holesin the atomizing head.

the fluidizing air velocity is controlled at an optimum 5 for goodfluidization. Too low a velocity will result in poor particlecirculation and hence a poor coating. Too high a velocity will promotemechanical breakdown of the particles and excessive particle carryoverfrom the body of the bed.

The temperature of the fluidizing air, and hence the temperature of thebed, is controlled within a critical range. Too low a temperatureresults in too low a rate of solvent evaporation to cause the particlesto become too wet, circulate poorly, and agglomerate. Too high atemperature tends to evaporate the solvent prematurely before thecoating solution contacts the particle to be coated. Normally thetemperature of the fluidizing air is such that the bed temperature isabout 80F to about 130F.

Particles coated by the above-described procedure are completelyencapsulated with a continuous coating, and are free-flowing andnon-agglomerated.

It is important that each particle be fully covered, particularly in thecase of the bleach compounds having releasable chlorine to be subjectedto treatment with a fixed alkali hydroxide, since contact thereof with achlorinated compound may result in a violent reaction.

When it is desired to apply a second, or outer, coating in accordancewith the invention, for example, when the core substance is achlorine-releasing agent to be used as a bleach in home-launderingoperations, the first coating will comprise a saturated fatty acid asdescribed hereinabove.

After removing the fatty acid coated particles from the fluidizer, theparticles are treated to apply an outer coating of an alkali metal oralkaline earth soap of the fatty acid which comprises the first coat.The outer coating is advantageously applied by gently agitating thefatty acid coated particles in an aqueous solution of an alkali metal oralkaline earth hydroxide having a concentration as set forthhereinafter, for about 10 minutes to about 2 hours, preferably for abouthour, and until the hydroxide reacts with at least a portion of thefatty acid, and completely encapsulates the aparticles with the reactionproduct of the fatty acid and the hydroxide The temperature of thehydroxide solution is suitably between about 35F and about 200F and isnot higher than the melting point, and preferably not higher than about5F below the melting point, of the particular fatty acid employed forthe first coat, and in any event not sufficiently high to melt the fattyacid.

Following the aforementioned treatment the double coated particles areseparated from the treating solution for example by decantation on ascreen, and dried to produce completely encapsulated, free-flowing,particles coated with a first or inner layer of fatty acid, and a secondor outer layer of the fixed alkali soap of the fatty acid.

The proportion of the fatty acid coating that is converted to thecorresponding soap is not critical. All that is required is that theencapsulating coat of the reaction product of the fatty acid and fixedalkali hydroxide, i.e., soap, completely cover each particle. Theinvention contemplates a process wherein some or all of the primaryfatty acid coat is converted to soap in the second coating step,provided that the conversion to soap proceeds at least to the extentthat the soap covers every particle completely. In a typical case, eachparticle will have on the surface thercofa first coating ofa fatty acidand a second, or outer, coating of the salt of the acid which comprisesthe first coat.

A critical feature of the second coating is the concentration of thealkali in the solution employed to react with the fatty acid. Theconcentration of sodium hydroxide should be between about 3 to about lpercent by weight when the primary coating is stearic acid or a mixtureof stearic and palmitic acids, and should be about to about percent whenthe primary coating is lauric acid or the commerical 95 percentmaterial. The concentration of potassium hydroxide should be betweenabout 10 and about l5 percent. Calcium hydroxide should be applied as asaturated solution, i.e., about 0.1 percent by weight. Below thecritical concentrations the coating becomes soft and gel-like, and isnot protective. At concentrations above the critical levels, this ofcourse not being applicable to calcium hydroxide, the particles tend torise due to the relatively higher density of the alkali solution and aredifficultto coat properly.

Preferred concentrations are about 3 to about 7 percent sodium hydroxidewhen the primary fatty acid coating is in the upper portion of thesoap-making molecular weight range, for example, palmitic and stearicacids, and about 12 to about 14 percent sodium hydroxide for the lowerportion, for example, when the fatty acid is lauric acid. The preferredconcentration of potassium hydroxide is about 10 to abut 13 percent, andof calcium hydroxide, about 0.1 percent.

The proportion of primary coating substance relative to thesingle-coated particle may be from about 25 to about 75 percent byweight, preferably about 50 percent. The conversion of fatty acid tosoap to form the outer coating adds very little to the weight ofcoating.

The advantages of the dual coating of the present invention (i.e.,protection without pinholing) appear to be brought about by a differentmechanism by which the bleach particles are made available to thewashing solution. When a fatty acid is the only coating, the release ofthe bleach particle depends upon the melting point of the coating ascompared to the temperature of the washing solution. When the meltingpoint of a fatty acid single coating material is the same or lower thanthe washing temperature, ther is severe color damage on colored fabrics(pinholing); when the melting point is higher than the washingtemperature no pinholing is discerned but the total available chlorinereleased from the coated particles is only about -60 percent of thetheoretical. In contrast, when particles of potassiumdichloroisocyanurate are provided with a dual coating in accordance withthe present invention, the bleach particles are released into thewashing solution by the relatively slow rate of solubility of the soapcoating, to remove as well the undercoating of fatty acid, possibly byan emulsifying action.

In accordance with the foregoing description, the process for coatingparticles of an oxidizing material having at least one reactive chlorineatom in its molecular structure comprises the steps of:

i. placing said particles in such a configuration as to define a layerthereof having a thickness between about inch and about 6 inches, on aperforated support,

ii. adjusting the height of a downwardly disposed spraying means capableof producing a spray of liquid droplets in a downwardly divergingpattern, to a level such that the outermost droplets of said spraycontact 5 said layer of particles at the perimeter thereof as defined bysaid layer in static state,

iii. causing a gas to flow upward through said perforated support,thereby expanding the thickness of said layer and maintaining saidparticles in continuous motion to form a fluidized bed,

iv. spraying a solution of a solidifiable fatty acid on said fluidizedbed until all particles in said bed are completely coated with saidfatty acid,

. treating said coated particles with an aqueous solution of a fixedalkali hydroxide selected from the group consisting of sodium hydroxide,potassium hydroxide, and calcium hydroxide, and mixtures thereof,thereby reacting said hydroxide with at least a portion of said fattyacid, and completely encapsulating said particles with the reactionproduct of said fatty acid and said hydroxide, the concentration of saidfixed alkali hydroxide in said solution being about 3 to about 15percent when said fixed alkali is sodium hydroxide, about 10 to about 15percent when said fixed alkali is potassium hydroxide, and about 0.1percent when said fixed alkali is calcium hydroxide, by weight of saidsolution.

Encapsulated particles of chlorine-releasing agent prepared inaccordance with the instant invention find utility in admixture withparticulate detergent compositions having therein an anionic or nonionicdetergent species that is not adversely affected by chlorine liberatedfrom the bleaching agent.

The dual-coated particles may be admixed with a particulare detergentcomposition. Examples of anionic detergents useful in thedetergent-bleach compositions of the invention are the higher alkylmononuclear aromatic alkalimetal sulfonates, such asalkylbenzenesulfonates having about 9 to about 18 carbon atoms in thealkyl group wherein the alkyl group is derived from polypropylene asdescribed by Lewis in U.S. Pat. No. 2,477,382, or wherein the alkylgroup is derived from kerosene, as described by Flett in U.S. Pat. No.2,390,295, and Rubinfeld in U.S. Pat. No. 3,320,174, or wherein thealkyl group is a straight chain and the benzene nucleus is randomlypositioned along the alkyl chain, as described in Baumgartner U.S. Pat.Nos. 2,723,240 and 2,712,530, and in U.S. Pat. No. 2,972,583, or whereinthe alkyl group is a hexene dimer or trimer as in McEwan U.S. Pat. No.3,370,100, or wherein the alkyl group is derived from alphaolefins, asin Swenson U.S. Pat. No. 3,214,462.

Also there may be employed primary and secondary alkyl sulfates, i.e.,RO-SO compounds wherein R represents an alkyl group having from 10 to 20carbon atoms such as sodium, potassium and magnesium lauryl sulfate,stearyl sulfate, coconut alkyl sulfate and tallow alkyl sulfate; N-longchain acyl-N-alkyl taurates and the salts thereof wherein the long chainis from 8 to 20 carbon atoms such as sodium oleoyl methyl taurate,sodium palmitoyl methyl taurate, sodium lauroyl methyl taurate and thecorresponding acyl ethyl taurates; long chain alkyl-oxyethylene sulfateswherein the long chain is from 8 to 20 carbon atoms such as sodium orlaurylpolyoxyethylene sulfate, sodium lauryloxyethylene sulfate andsodium cetylpolyoxyethylene sulfate; long chain alkyl aryl oxyethylenesulfates wherein the long chain is from 8 to 20 carbon atoms such asammonium, sodium or potassium nonyl octyland tridecylphenoxy monoandpolyoxyethylene sulfates; long chain acylisethionates wherein the longchain is from 8 to 20 carbon atoms such as sodium or potassiumlauroylstearoyl isethionate; alkaneor alkenesulfonates containing 8 to20 carbon atoms in the alkane or alkene group such as sodium orpotassium octane-, decane-, tetradecanc-, octadecanesulfonate andoctene-, decene-, tetradeceneand octadecenesulfonate;alkoxyhydroxyalkanesulfonates wherein the long chain is 8 to 22 carbonatoms such as lauryloxyhydroxypropanesulfonate,stearyloxyhydroxyethanesulfonate and tallowoxyhyroxypropanesulfonate;and fatty acid monoglycer idesulfates wherein the long chain is 8 to 22carbon atoms such as lauric-, myristic-, palmitic and stearicmonoglyceride sulfates; alpha-sulfo soap, such as disodium salt ofalpha-sulfo fatty acids wherein the fatty acids are derived from tallow,the sulfosuccinates, such as dioctyl sulfosuccinate, sodium salt, thesulfuric acid esters of polyhydric alcohols incompletely esterified withhigher fatty acids, such as the sodium salt of sulfated coconut oilmonoglyceride, and compounds known as Medialans, which are amidocarboxylic acids formed by condensing fatty acids of C -C chain lengthwith sarcosine, CH NH CH COOH. Generally the alkali metal salts areemployed.

The soaps are included within the definition of anionic detergents asused herein. Operable soaps within the present invention are the sodiumand potassium salts of acyclic monocarboxylic acids having chain lengthsof about 8 to about 22 carbon atoms. Particularly useful are the saltsof unsubstituted fatty acids derived from natural triglycerides, such astallow, palm oil, cottonseed oil, olive oil, lard, rapeseed oil, etc,,and the so-called high-lauric oils," generally exemplified by thetropical nut oils of the coconut oil class, including in addition tococonut oil, palm kernel oil, babassu oil, ouri curi oil, tucum oil,cohune nut oil, and murumuru oil, and for present purposes, ucuhubabutter, a triglyceride high in myristic acid esters. A particularlyuseful soap is one prepared from a mixture of about 80 percent tallowand about 20 percent coconut oil.

Preferably the detergent composition should be substantially free ofcompounds containing amino nitrogen to avoid adverse effects during thewashing operation.

Other suitable anionic synthetic detergents for use in the presentinvention can be found in the literature, such as Surface Active Agentsand Detergents" by Schwartz, Perry and Berch published by lntersciencePublishers, the disclosures of which are incorporated by referenceherein.

The water-soluble polyetheneoxy nonionic organic detergent compoundssuitable for use in the practice of the invention may be characterizedbroadly as ethylene oxide condensates of organic hydrophobic compoundsbearing a labile hydrogen atom in a polar substituent, said organichydrophobic compounds being within a molecular weight range such thatwhen serving as a base for a resulting ethylene oxide condensate, saidcondensate is capable of having detergent properties at a sufficientlyhigh ethylene oxide content.

Suitable hydrophobic bases falling within the foregoing description arealiphatic alcohols and mixtures thereof having from about 10 to aboutcarbon atoms, corresponding to an average molecular weight of about 158to about 228. The alcohol is preferably straight-chain but may contain 0to about 25 percent lower alkyl branching, mainly methyl, with some 2 3carbon alkyl groups, on the 2-position carbon of the alcohol molecule.

Other suitable hydrophobic compounds include a. the polyoxypropylencdiols which form the hydrophobic base of the Pluronics. "Pluronic" is atrademark of the Wyandotte Chemical Corp. the aforementioned hydrophobicbase is water-soluble and has a molecular weight from about 1,500 toabout 1,800.

b. Alkylphenols having an alkyl group of about 6 to about 12 carbonatoms. The alkyl group may be straight or branched and may be derivedfrom a propylene polymer, diisobutylene, hexene, nonene, or dodecene,for example, or mixtures of these. The ethylene oxide content of thedetergent molecule may range from 52 to about 80 percent by weight,preferably from about 60 to about percent by weight.

Among the water-soluble polyetheneoxy organic nonionic detergentcompounds useful in the combinations of the instant invention are l.condensates of ethylene oxide and a primary or secondary alkanol havingabout 8 to about 16 carbon atoms, the proportion of combined ethyleneoxide being from about 52 to about percent by weight, and mixturesthereof.

2. condensates of ethylene oxide and an alkanol having 14-15 carbonatoms with about 25 percent 2-methyl branching, the proportion ofcombined ethylene oxide in said condensate being from about 52 to about80 percent by weight, and mixtures thereof.

3. condensates of ethylene oxide and a hydrophobic base selected fromthe group consisting of the reaction product of propylene oxide andpropylene glycol, said reaction product having a molecular weight ofabout 1,800.

The water-soluble polyetheneoxy organic nonionic detergent compounds mayinclude:

1. Poly (ethylene oxide) condesates of primary or secondary aliphaticalcohols having about 11 to about 15 carbon atoms, said condensateshaving an average of about 9 molar proportions of ethylene oxide permole of alcohol, and mixtures thereof.

2. Poly (ethylene oxide) condensates of primay aliphatic alcohols havingabout 12 to about 15 carbon atoms and having about 25% lower alkylbranching on the 2-carbon, said condensates having an average of about 9to about 20 molar proportions of ethylene oxide per mole of alcohol, andmixtures thereof.

3. A condensate of 1 mole of octylphenol and about 7 -8 molarproportions of ethylene oxide.

4. Poly (ethylene oxide) condensates oflinear primary alcohols havingabout l4l 5 carbon atoms, and averaging about 13.5 carbon atoms, andhaving about 25 percent lower alkyl branching on the 2-carbons, saidcondensates having an average of about 13.5 molar proportions ofethylene oxide per mole of alcohol.

5. The poly (ethylene oxide) condensates of alkylphenols, e.g., thecondensation of products of alkylphenols having an alkyl groupcontaining from about 6 to 12 carbon atoms in either a straight chain orbranched chain configuration, with ethylene oxide, said ethylene oxidebeing present in amounts equal to 6 to 25 moles of ethylene oxide permole of alkylphenol. The alkyl substituent in such compounds may bederived from polymerized propylene, diisobutylene, octene, dodecene, ornonene, for example.

6. Compounds formed by the simultaneous polymerization of propyleneoxide and ethylene oxide, and containing randomly positioned propeneoxyand etheneoxy groups.

As examples of specific nonionic detergent compounds finding utility inaccordance with the invention, there may be mentioned:

A. branched-chain nonyl phenol condensed with about 8l4 molarproportions of ethylene oxide,

B. a mixed C C secondary alcohol condensed with 9-14 molar proportionsof ethylene oxide, the mixed secondary alcohols having the followingapproximate chain-length distribution:

2% c, 15% C 21% C 23% c, 17% c 15% C C. a mixed C -C alcohol made by the0x0 process condensed with about 9-15 molar proportions of ethyleneoxide, and

D. a mixture of about 65% C and about 35% C synthetic straight-chainprimary alcohols condensed with about 9-15 molar proportions of ethyleneoxide. The ternary compositions of the present invention may beformulated with a detergent builder as a detergency aid, for example,those mentioned hereinafter, to provide a commercially valuabledetergent-bleach composition.

The term builder as used herein refers to any substance compatible with,and assisting the detergency of the aforementioned ternary combination.

Suitable builder compounds are tetrasodium and tet rapotassiumpyrophosphate, pentasodium and pentapotassium tripolyphosphate, sodiumor potassium carbonate, sodium or potassium silicates having an SiO Na Oratio of about 1:1 to about 3.2:1, hydrated or anhydrous borax, sodiumor potassium sesquicarbonate, phytates, polyphosphonates such as sodiumor potassium ethane-l-hydroxy-l, l-diphosphonate, etc.

Also useful are other organic detergent builders such as the sodium orpotassium oxydisuccinates, sodium or potassium oxydiacetates,carboxymethyloxysuccinates, hydrofuran tetracarboxylates, ester-linkedcarboxylate derivatives of polysaccharides, such as the sodium andpotassium starch maleates, cellulose phthalates, semicellulosediglycolates, starch, oxidized heteropolymeric polysaccharides, etc, Theweight percent of the builder present in the built anionic detergentcomposition is from an amount of about 6 and up to about 90 percent fromabout to about 60 percent. Suitably, a builder may be present in theratios of about 0.5 to about 10 parts by weight, preferably about 2 toabout 5 parts by Approximate Percentage Anionic or nonionic detergentl-'7z Builder O-907: Encapsulated bleaching agent 2-257z Opticalbrightener 0().371 Sodium carboxymethylccllulosc 0-172 Water 545% Sodiumsulfate 02571 Detergent compositions formulated for use in the washingof fabrics in automatic washing machines may contain about 5 to about 30percent anionic detergent, about 30 to about 60 percent of one or moreof the builders mentioned hereinabove, and sufficient encapsulatedbleaching agent to provide 30-200 parts per million chlorine in the washwater, or approximately 2 to 25 percent of the agent in the detergentformulation. Usually included are about 0.1-0.3 percent opticalbrightener, and about 0.4 percent sodium sulfate, and if desired smallproportions of other components such as germicides, anti-caking agents,etc. to confer special properties on the product.

When the detergent is soap, and comprises the major proportion of thedetergent-bleach product, the soap may be present in amounts from about60 to about 90 percent little or no builder being required, althoughabout 1 to about 10 percent of an alkaline builder may be advantageous.

When the detergent is nonionic, from about 5 to about 20 percent issuitable, the balance of the composition being as listed above.

Detergent compositions formulated for mechanical dishwashers and havingthe encapsulated bleaching agents of the invention therein may containlow proportions of nonionic detergent, for example about 1 to about 4percent, and may contain a suds depressant and a high proportion of abuilder, for example about 50-90 percent of a mixture of sodiumtripolyphosphate, sodium carbonate, and sodium silicate.

The invention may be more fully understood by reference to the followingexamples.

EXAMPLE 1 This example describes a dual-coating process within theinvention.

Thirteen pounds of extra coarse grade potassium dichloroisocyanurate arecharged onto the perforated plate of the cylindrical coating tower 1(FIG. 1). The perforated plate is a 60-mesh stainless steel screen. Theparticles are fluidized and suspended by an upwardly moving air streamsupplied by blower 10. The superficial air velocity of the fluiding airstream is 8.5 feet per second. The temperature of the air is maintainedat 95 2F, by heat exchanger 11.

The primary coating solution is prepared by dissolving triple-pressedstearic acid (about 45 percent stearic acid) in methylene chloride toform a 20 percent solution. A small amount of ultramarine blue isdissolved in the coating solution for subsequent use in observing thecontinuity of the primary coating.

The primary coating solution is sprayed on the fluidized particles 3,through nozzle 5, appropriately adjusted as to height. Nozzle 5 has sixorifices disposed to provide the desired diverging spray pattern. Anauxiliary stream of air is applied to the fluidized bed through 9nozzles horizontally disposed at the perforated support screen levelwith the tips of the nozzles placed close to the inner wall of thetower. The air leaves these nozzles in a horizontal path substantiallytangential to the wall of the tower. It is the function of thistangential air to assist in keeping in motion the particles at the outerperiphery of the plate which do not obtain the full effect of thefluidizing air.

The coating solution is applied to the fluidized particles for a periodof 2 hours. The weight of the coating is about equal to the weight ofthe original particles. The coated particles are of uniform blue colorand size, with substantially no agglomeration, and are dry andfree-flowing. When some of the coated particles are left immersed for 2days in an acidified potassium iodide solution, no color change isobserved, indicating complete encapsulation of the particles.

The second coating is applied in the following manner.

A 5.2% sodium hydroxide solution is prepared by diluting 60 grams of 50%NaOH solution with 520 grams of distilled water in a two-liter beaker.The dilute solution is heated to 100F in a water bath and 200 grams ofthe particles coated as described above are placed in the NaOH solutionand gently agitated for 30 minutes, maintaining the temperature of thesolution between 105F and 110F. The molar ratio of NaOH to fatty acid is2:1. After the 30-minute treatment, the solution is decanted through a25-mesh stainless steel screen, and the particles on the screen aredried at room temperature for 24 hours. The particles are free flowingand white, indicating complete covering of the bluecolored first coat.

The singleand double-coated particles are tested for east of chlorinerelease and for adverse effect on cloth in the following manner.

Six pounds of white cotton fabric are placed in a toploading automaticwashing machine. Three swatches of blue denim cloth and one swatch ofblack 65/35 Dacron/cotton cloth, each measuring 12 X 12 inches areplaced on top of the cotton cloth in circular configuration. Next, thereis placed directly on the fabric 3.4 ounces of a detergent-bleachcomposition containing 8.0percent of the encapsulated material preparedas above. Water at a temperature of 132F :3F is run directly on thedetergent-bleach composition for about 6 150 seconds to a volume of 17.4gallons. The wash solution is agitated for minutes, and the fabrics areexamined. The results are shown in Table 1.

Single Coat with Fatty Acid Fatty Acid (A) Fatty Acid (B) Fatty Acid (C)Dual Coat First Coat Fatty Acid (A) 2.85% NaOH 21.03 2

10 min. 5.34% NaOH 30 min. 10.33% NaOH 30 min.

not determined 23.19 1 69.83

(A) about 4571 stearic acid and 5571 palmitic acid;

m.p. 13ll32F (B) 95% palmitic, 4'7 stearic, 17: myristic acids;

m.p. 138-144F (C) about 70% stearic acid and 3071 palmitic acid;

m.p. 138.5l43F Pinholing Rating 0 none (excellent) 1 minimal pinholing(acceptable) 2 severe pinholing (unacceptable) very severe pinholing(unacceptable) From the foregoing data in Table l, is may be seen that asingle coating of fatty acid is inadequate to accomplish the dualpurpose of providing a high chlorine release and at the same time avoidpinholing. It will be noted that fatty acid (A) having a melting pointbelow the temperature of the wash water, melts to release all of thechlorine in the encapsulated material, but causes pinholing, due tocontact of the encapsulated material with the fabric upon the melting ofthe fatty acid coating. Fatty acids (B) and (C), having melting pointsabove the temperature of the wash water, are unsatisfactory, since theydo not allow a sufficient release of chlorine to be of any value as ableach, although the low level of chlorine release prevents pinholing.

Again referring to the foregoing data, it will be observed that a dualcoating applied in accordance with the invention prevents pinholing to asubstantial extent, and additionally allows an adequate release ofchlorine.

EXAMPLE 2 This example further illustrates the present process forapplying a first coat of fatty acid to particles of potassiumdichloroioscyanurate.

A coating solution is prepared in vessel 6 by dissolving 10 pounds offatty acid (about 70% stearic acid and palmitic acid) in pounds ofmethylene chloride. Twenty grams of blue pigment is added and thesolution warmed at 95F.

Ten pounds of extra coarse grade potassium dichloroisocyanurate isscreened to 25 mesh and placed on the 40-mesh supporting screen incoating tower 1 (FIG. 1). Fluidizing air is forced into the apparatusthrough duct 9 at a superficial air velocity of 6. 8 feet per second.Tangential air is supplied as needed. The temperature of the bed ismaintained at 107 i 2F.

The coating solution is sprayed downward onto the fluidized bed througha 6-hole atomizing nozzle located 12 inches above the supporting screen.The coating is applied at the rate of 6.7 pounds per hour, and thesolvent is evaporated at the rate of 23 pounds per hour.

The coated product is a dry, nonagglomerated, freeflowing particulatesolid of which the particles are substantially uniform in size. A testin potassium iodide solution indicates that the particles are completelycovered.

After storing for 8 weeks at 80F and 80 percent relative humidityadmixed with particles of a commercial detergent, substantially no lossof chlorine occurs. A

control wherein the potassium dichloroisocyanurate is uncoated loses 90percent of its chlorine.

EXAMPLE 3 This example illustrates the coating of sodium perborate withpolyethylene glycol, m.w. 6,000.

The process follows that described in Example 1, except that 10 poundsof coarse grade sodium perborate is used as the core material, and thecoating material is polyethylene glycol, m.w. 6,000 applied from a 20%solution in methanol. A small amount of Congo Red dye is dissolved inthe methanol for subsequent use in judging the continuity of thecoating. The weight ratio of coating to core material is 1:2, that is,the coated particles have one-third coating material by weight. Thisrequires 25 pounds of coating solution, or 20 pounds of solvent, i.e.,methanol, to be evaporated. The evaporation is accomplished in 2 hoursat a bed temperature f 8090F, and a final fluidizing air velocity of 6.8feet per second. The bed of perborate particles is 2 inches thick beforefluidizing. The coating solution is applied from a nozzle located 1 footfrom the top of the 2-inch thick bed.

. EXAMPLE 4 The process of this example is the same as that of Example3, except that the coating material is polyvinylpyrrolidone having amolecular weight of 15,000, and the air velocity of the fluidizing airis 4.3 feet per second.

EXAMPLE 5 A spray-dried detergent composition having the followingforr'nula is prepared by conventional procedures.

To separate portions of the above-described compositions are mixedvarious proportions of the dualencapsulated product of Example 1, theproportions being as follows.

Parts By Weight Example No. 5A 5B 5C SD SE Spray dricd composition 80 8488 92 96 Product of Example 1 l6 l2 8 4 EXAMPLE 6 A composition suitablefor use in mechanical dishwashers and having the following formula isprepared by conventional 71 Nonionic detergent "A condensate of amixture of primary aliphatic alcohols having about l2-l5 carbon atomswith about 25% lower alkyl branching on the 2 carbon, and about 9 molarproportions of ethylene oxide.

EXAMPLE 7 This experiment shows the effect of coating temperature on thesecond coat of potassium dichloroisocyanurate when the second coatingsolution is a solution of potassium hydroxide. The first coat is appliedas in Example 1. The second coat is applied under a variety ofconditions, namely at several concentrations and at temperatures of Fand F. The results of these tests show that a satisfactory dual coatingis obtained when the second coating is applied from a 10 percentsolution of KOH at a temperature of 85F. However, at a temperature of F,the second coating becomes gel-like when the KOH concentration is lessthan 10 percent, and cracks upon drying when the KOH concentration is15-20 percent.

EXAMPLE 8 This example illustrates the effect of sodium hydroxideconcentration of from 3 to 10 percent in the solution employed forapplying the second coating to particles of potassiumdichloroisocyanurate.

In this experiment the fatty-acid-coated particles are treated with thealkali solution at a temperature of 110F and a reaction time of 30minutes, other test conditions being as described in Example 1. Theweight of total coating is approximately the same as the weight ofstarting core substance.

Eight parts by weight of the double coated potassiumdichloroisocyanurate are admixed with 92 parts by weight of aspray-dried detergent composition having the formula set forth inExample 5. The mixture is tested in a washing machine at a wash-watertemperature of F and a 12-minute agitation, other conditions being asdescribed in Example 1. During the washing period, the wash solution isanalyzed for oxidizing chlorine, and from this figure is calculated thepercentage of available chlorine in the mixture that is released.Samples are taken and analyzed 1%, 2, 5, 8, l0 and 12 minutes after thestart of the agitation of the wash solution. At the end of the test, thedenim swatches are visually observed for pinholing. The results areprovided in Table II, below. It will be noted that the concentration ofthe sodium hydroxide in the solution used to apply the second coat tothe particles has no effect on the percentage of chlorine releasedduring use. Pinholing is virtually absent when the second coat isapplied from a 3-7 percent sodium hydroxide solution, and is greatlyreduced when the concentration is 8l0 percent.

TABLE 11 -PlNHOl.E TEST AND AVAILABLE CHLORlNF. RELEASE Concentration of"/1 Chlorine Released NaOH Used Available "Pinholing"' Example to ApplySecond Coat Chlorine ('71) Rate 30 sec. 2 min. 5 8 12 min.

7a 371 NaOH 26.14 0-1 16.88 52.17 80.26 89.13 89.12 89.07 7h 4'71 24.790-1 0 43.22 50.49 76.47 90.44 89.57 71: 57: 24.50 0-] 4.38 43.35 89.0489.04 95.6 92.51 7d 6% 26.10 01 0 39.73 56.86 77.41 89.32 90.27 70 7'7:27.95 0-1 5.58 56.58 86.32 90.50 91.05 93.23 71 8% 28.32 12 19.23 49.2478.07 93.26 93.54 90.36 7g 97! 30.29 1-2 20.43 75.08 90.69 8731 93.1087.81 7h 10% 27.92 1-2 14.17 63.50 92.23 89.41 94.95 90.0

Notes: 'Pinholing Rate" 0 No pinholing (excellent) 1 Pinholing observed(acceptable) 2 Severe pinholing EXAMPLE 9 to storage ranges from 1.95 to2.16 percent, with a This example illustrates the substantially completestability of potassium dichloroisocyanurate having a double coating inaccordance with the present invention.

To separate portions of the spray-dried detergent composition having theformula of Example 5 are added double coated particles of potassiumdichloroisocyanurate prepared by the process of Example 1, the coatedparticles added to one portion having had the second coat applied from a5% NaOH solution, and the coated particles added to the other portionhaving had mean value of 2.04 percent, basis mixture of detergentcomposition and dichloroisocyanurate. The stored mixtures are sampledand analyzed for available chlorine content after l, 2, 4 6, 8 and 12weeks, one carton of each mixture being removed from storage for aduplicate analysis at each of these periods. The results, presented inTable 111, show that the uncoated potassium dichloroisocyanurate losesabout 15 percent of its available chlorine under the aforementionedstorage conditions while the double coated dichloroisocyanurate losesonly about 2 percent to about 2.5 percent of its available chlorine. Theprotection afforded by the second coating whether applied from a 5percent NaOH solution is substantially the same.

TABLE 111 AVERAGE AVAlLABLE CHLORlNF. AND '2 AV. CHl.ORlNE LOSS ablechlorine, basis total mixture. A control mixture is prepared whereinuncoated potassium dichloroisocyanurate is mixed with the detergentcomposition of Example 5 in a proportion to provide approximately 2percent available chlorine.

Six cartons of each of the three aforesaid mixtures are prepared, eachcarton containing 400 grams of the total mixture. The base detergentcomposition and the bleach component are separately added to each cartonto avoid sampling and segregation errors which might be possible if thecartons were filled from a larger bulk mixture. The contents of eachcarton are blended in a Bleach Z Av. Chlorine Storage Time Component andits Loss 0 Wk. 1 Wk. 2 Wk. 4 Wk.. 6 Wk 8 Wk. 12 Wk.

Uncoatcd 71 Av. Chlorine 2.04 1.83 1.83 1.81 1.78 1.69 1.74 71- Loss0.00 10.29 10.29 11.27 12.75 17.16 14.71 Coated"" 71 Av. Chlorine 2.042.16 1.99 v 1.94 2.10 1.98 2.00 "/7 Loss 0.00 3.43 2.45 4.90 2.94 2.941.96 Coatcd" "/1 Av. Chlorine 2.04 1.97 1.94 1.93 2.1 l 2.03 1.99 7?Loss 0.00 3.43 4.90 5.39 3.43 0.49 2.45

""Second coating applied from a 5% solution of NaOH ""Second coatingapplied from a 1071 solution of NaOH composition is such as to provideabout 2 percent avail- EXAMPLE 10 This example shows the effect onstability of coated and uncoated chlorinated cyanurates admixed with adetergent composition when stored variously in open wax-laminatedbarrier cartons and in open and closed non-barrier cartons, i.e.,allowing free or only partially restricted passage of vapors.

Mixtures are prepared, stored and analyzed as described in Example 8,with the exception that the second coating, when applied, is appliedfroma 6% NaOH solution, and other exceptions identified as follows:

rotating mixer. The cartons are wax laminated to provide a vaporbarrier. Ex. Core Coating Carton Each sample is stored in theaforementioned ca t s 9a Potassium dichloroisocyanurate Double Barriertype in sealed condition at a temperature of 80F and 80permp centhumidity. Prior to sealing, two weighed samples 9b Pmassmmdlchlormsocydnurate as? are removed from two cartons of each of thethree mixp 1 tures and analyzed for available chlorine content. ThePmassium dlchlomisocyanurale w fir analysis shows that the availablechlorine content prior Closed top After 2 weeks storage at 80F and 80percent relative humidity, the chlorine losses are determined. Theprotective action of the double coating as compared with uncoatedparticles of chlorine bleaching agent is evident from the data set forthbelow:

Storage Time Example Week 2 Weeks 9a "/1 Chlorine 2.31 2.26

% Loss 21 9b 72 Chlorine 2.28 2.21

7r Loss 3.1

9c Chlorine 2.29 2.28

7r Loss 0.4

9d 72' Chlorine 2.09 0.96

Z Loss 54.1

9e 7r Chlorine 2.01 1.99

7: Loss 1.5

9f Chlorine 2.08 1.75

'7( Loss 15.9

9g "/1. Chlorine 1.99 1.86

% Loss 6.5

Having described the invention, modifications within the purview thereofwill occur to those skilled in the art, and accordingly the invention isto be limited only within the scope of the appended claims.

What is claimed is:

l. A process for coating particles of an oxidizing material having atleast one reactive chlorine atom in its molecular structure comprisingthe steps of:

i. placing said particles in such a configuration as to define a layerthereof having a thickness between about 9% inch and about 6 inches, ona perforated support,

ii. adjusting the height of a downwardly disposed spraying means capableof producing a spray of liquid droplets in a downwardly divergingpattern, to a level such that the outermost droplets of said spraycontact said layer of particles at the perimeter thereof as defined bysaid layer in static state,

iii. causing a gas to flow upward through said perforated support,thereby expanding the thickness of said layer and maintaining saidparticles in continuous motion to form a fluidized bed,

iv. spraying a solution of a solidifiablc fatty acid on said fluidizedbed until all particles in said bed are completely coated with saidfatty acid, and

v. treating said fatty-acid coated particles with an aqueous solution ofa fixed alkali hydroxide selected from the group consisting of sodiumhydroxide, potassium hydroxide, and calcium hydroxide, and mixturesthereof, said treatment comprising a. agitating said fatty acid-coatedparticles in said aqueous hydroxide solution for about 10 to aboutminutes at a temperature of about 85F to about F, and not higher thanabout 5F below the melting point of said fatty acid, thereby reactingsaid hydroxide with at least a por tion of said fatty acid, theconcentration of said fixed alkali in said solution being about 3 toabout 10 percent when said alkali is sodium hydroxide, about 10 to about15 percent when said fixed alkali is potassium hydroxide, and about 0.1percent when said fixed alkali is calcium hydroxide, by weight of saidsolution.

2. A process in accordance with claim 1 wherein said fatty acid is amember selected from the group consisting of palmitic and stearic acidsand mixtures thereof, and said aqueous solution of fixed alkalihydroxide in a solution of about 3 to about 10 percent sodium hydroxideby weight of said solution.

3. A process in accordance with claim 1 wherein said fatty acid issubstantially lauric acid and said aqueous solution of fixed alkalihydroxide is a solution of about 10 to about 15 percent sodium hydroxideby weight of said solution.

4. A process in accordance with claim 1 wherein the concentration ofsaid sodium hydroxide is about 3 percent NaOH by weight, solution basis.

5. A process in accordance with claim 1 wherein the concentration ofsaid sodium hydroxide solution is about 6% NaOH by weight, solutionbasis.

6. A process in accordance with claim 1 wherein the concentration ofsaid sodium hydroxide solution is about 10% NaOH by weight, solutionbasis.

7. A process in accordance with claim 1 wherein the concentration ofsaid potassium hydroxide is about 10 to about 13 percent.

8. A process in accordance with claim 1 wherein said oxidizing materialhaving at least one reactive chlorine atom in its molecular structure ispotassium dichloro-

1. PROCESS FOR COATING PARTICLES OF AN OXIDIZING MATERIAL HAVING ATLEAST ONE REACTIVE CHLORINE ATOM IN ITS MOLECULAR STRUCTURE COMPRISINGTHE STEPS OF: I. PLACING SAID PARTICLES IN SUCH A CONFIGURATION AS TODEFINE A LAYER THEREOF HAVING A THICKNESS BETWEEN ABOUT 1/2 INCH ANDABOUT 6 INCHES, ON A PERFORATED SUPPORT. II. ADJUSTING THE HEIGHT OF ADOWNWARDLY DISPOSED SPRAYING MEANS CAPABLE OF PRODUCING A SPRAY OFLIQUID DROPLET IN A DOWNWARDLY DIVERGING PATTERN, TO A LEVEL SUCH THATTHE OUTERMOST DROPLETS OF SAID SPRAY CONTACT SAID LAYER OF PARTICLES ATTHE PERIMETER THEREOF AS DEFINED BY SAID LAYER IN STATIC STATE, III.CAUSING A GAS FLOW UPWARD THROUGH SAID PERFORATED SUPPORT, THEREBYEXPANDING THE THICKNESS OF SAID LAYER AND MAINTAINING SAID PARTICLES INSAID BED ARE COMPLETELY FORM A FLUIDIZED BED, IV. SPRAYING A SOLUTION OFA SOLIDIFIABLE FATY ACID ON SAID FLUIDIZED BED UNTIL ALL PARTICLES INSAID BED ARE COMPLETELY COATED WITH SAID FATTY ACID, AND V. TREATINGSAID FATTY-ACID COATED PARTICLES WITH AN AQUEOUS SOLUTION OF A FIXEDALKALI HYDROXIDE SELECTED FROM THE GROUP CONSISTING OF SODIUM HYDROXIDEPOTASSIUM HYDROXIDE, AND CALCIUM HYDROXIDE, AND MIXTURES THEREOF, SAIDTREATMENT COMPRISING A. AGIATING FATTY ACID-COATED PARTICLES IN SAIDAQUEOUS HYDROXIDE SOLUTION FOR ABOUT 120 MINUTES AT TEMPRERATURE OFABOUT 85*F TO ABOUT 130*F, AND NOT HIGHER THAN ABOUT 5*F BELOW THEMELTING POINT OF SAID FATTY ACID, THEREBY REACTING SAID HYDROXIDE WITHAT LEAST A PORTION OF SAID FATTY ACID, THE CONCENTRATION OF SAID FIXEDALKALI IN SAID SOLUTION BEGIN ABOUT 3 TO ABOUT 10 PERCENT WHEN SAIDALKALI IS SODIUM HYDROXIDE, ABOUT 10 TO ABOUT 15 PERCENT WHEN SAID FIXEDALKALI IS POTASSIUM HYDRXIDE, AND ABOUT 0.1 PERCENT WHEN SAID FIXEDALKALI IS CALCIUM HYDROXIDE, BY WEIGHT OF SAID SOLUTION.
 2. A process inaccordance with claim 1 wherein said fatty acid is a member selectedfrom the group consisting of palmitic and stearic acids and mixturesthereof, and said aqueous solution of fixed alkali hydroxide in asolution of about 3 to about 10 percent sodium hydroxide by weight ofsaid solution.
 3. A process in accordance with claim 1 wherein saidfatty acid is substantially lauric acid and said aqueous solution offixed alkali hydroxide is a solution of about 10 to about 15 percentsodium hydroxide by weight of said solution.
 4. A process in accordancewith claim 1 wherein the concentration of said sodium hydroxide is about3 percent NaOH by weight, solution basis.
 5. A process in accordancewith claim 1 wherein the concentration of said sodium hydroxide solutionis about 6% NaOH by weight, solution basis.
 6. A process in accordancewith claim 1 wherein the concentration of said sodium hydroxide solutionis about 10% NaOH by weight, solution basis.
 7. A process in accordancewith claim 1 wherein the concentration of said potassium hydroxide isabout 10 to about 13 percent.
 8. A process in accordance with claim 1wherein said oxidizing material having at least one reactive chlorineatom in its molecular structure is potassium dichloroisocyanurate.